The invention relates to a wind turbine, more specifically to a rotor assembly for a wind turbine.
Wind turbines are often used to generate electrical energy from electrical energy by converting the kinetic energy of the wind. A wind turbine comprising a horizontal shaft comprises a tower, a stator and a rotor assembly with a plurality of vanes. The rotor assembly is mounted in the pod by means of a shaft which is directly or indirectly connected to a generator for generating electrical energy.
A known wind turbine is described in US2009/0208337, which discloses a wind turbine with a rotor assembly. Said rotor assembly comprises a central hub with a central rotation axis and a plurality of vanes, each of which is attached to the central hub by its central end and the longitudinal axis of which extends substantially radially with respect to the central rotation axis up to their radial end. The vanes comprise a two-part structure with an intermediate point situated between the central end and the radial end. The vanes comprise a central vane part which extends from the central end to this intermediate point. Furthermore, the vanes also comprise a radial vane part which is attached to the central vane part and extends from the intermediate point to the radial end of the vane. Furthermore, this rotor assembly comprises a cable system which cooperates with the vanes and the central hub. Both vane parts have a wing shape and particularly the wing shape of the central vane part results in a risk of interference with the cable system, in particular the pair of cables of each vane which is situated between the intermediate point and the central hub. In addition, the intermediate points of the various vanes are also connected to each other by means of a cable. This connection causes undesirable peak loads resulting from interference of deformations and vibrations of the various vanes in the plane of rotation of the vanes.
Another such wind turbine is known from CN101235795B, which discloses a wind turbine with a rotor assembly comprising a central hub 1, with a tapered pipe flange Z from which vanes extend radially comprising a two-part structure as explained above with a central vane part A and a radial vane part B attached at an intermediate point C1. Each of these vane parts A and B is shaped as a wing. In addition, the intermediate points of the various vanes are also connected to each other by means of a big ring C shown in FIG. 1 in dot striped lines. This increases the complexity and the weight of the rotor assembly. This connection also causes undesirable peak load resulting from interference of deformations and vibrations of the various vanes in the plane of rotation of the vanes. The cable system of CN101235795B comprises three cables 2, 3, 4 per vane. These cables being attached between vane attachment points at the intermediate point C1 and hub attachment points at the location of the central hub 1 and its tapered pipe flange Z. These three cables 2, 3, 4 are aligned with the longitudinal axis of their vane, viewed along the central rotation axis. Two of these three cables 3, 4 are on either side of the plane covered by the longitudinal axis of their vane. The tapered pipe flange Z and the third cable attached increases complexity of the construction of the central hub 1, and further more when used in an off-wind setup in which the rotor assembly is situated downstream of the mast along the wind direction during operation, cable 4 is the one exposed to the highest load as it is exposed to a tension load, while the cables 2 and 3 are exposed to a pressure load which reduces the load in these cables.
Another such wind turbine is known from DE19606359, this mechanism uses a linkage system of which the linkages are connected at one end to the rotor at approximately the same point where the vane is connected to the rotor; and the linkages are connected at their other end to the wing of the vane. This does not allow the use of a vane comprising a wing rotatable along the longitudinal axis of the vane. It further causes the risk of generating large torsional forces at the connection points of the vane and the linkage system.
It is known from WO13007359A1 produce a wing for use in such a windturbine by means of an extrusion process which makes use of a rotating extrusion die or of a subsequent twisting operation to provide a wing with a twisted shape along the longitudinal direction of about 3 to 5 degrees per meter. However the use of such a rotating extrusion die complicates the extrusion process and a subsequent twisting operation does not always result in a sufficiently uniform twist along the entire length of the wing.